Averaged and time-resolved heat transfer of steady and pulsating entry flow in intake manifold of a spark-ignition engine

Abstract

Abstract Entry flow heat transfer experiments are reported in steady and pulsating flows of air at mean Reynolds numbers of 3000–35,000. The ducts are chosen to match typical spark-ignition engine manifolds: a highly curved and a straight pipe, which together bracket most practical geometries. The pulsating engine intake flow encompasses an approximate half sine wave followed by a stagnant phase three times as long, all at a repetition rate of 16–50 Hz. Heat flow is imposed through electric heating of the outsides of the manifolds. Heat transfer in the curved pipe is closely comparable to the straight geometry, and it is concluded that entrance effects dominate. Time-averaged axially resolved and axially averaged Nusselt numbers are reported. The unsteady nature of the intake flow enhances heat transfer significantly, between 50% and 100%. Time-resolved wall heat flux measurements at a location close to the exit of the system show that heat transfer is delayed relative to the onset of the flow. During the stagnant flow phase, heat transfer and turbulence decay slowly from their high levels during the induction flow phase. Heat transfer enhancement in the pulsating flow case is caused by the contribution of the stagnant phase.